﻿204 
  INTRODUCTION 
  TO 
  BOTANY 
  

  

  of 
  securing 
  this 
  nutriment 
  result 
  in 
  partial 
  or 
  complete 
  break- 
  

   ing 
  down 
  of 
  the 
  food 
  substance. 
  This 
  is 
  known 
  as 
  decay. 
  

   While 
  a 
  body 
  is 
  undergoing 
  decay, 
  usually 
  several 
  kinds 
  of 
  

   bacteria 
  and 
  other 
  organisms 
  live 
  in 
  turn 
  upon 
  it. 
  In 
  com- 
  

   plete 
  decay 
  all 
  of 
  the 
  nutrient 
  organism 
  is 
  used 
  as 
  food, 
  or 
  

   passes 
  into 
  the 
  air 
  as 
  gases, 
  or 
  is 
  dissolved 
  in 
  water 
  and 
  

   carried 
  into 
  the 
  earth 
  or 
  into 
  streams. 
  The 
  materials 
  that 
  re- 
  

   sult 
  from 
  decay 
  are 
  not 
  only 
  directly 
  the 
  remnants 
  of 
  the 
  orig- 
  

   inal 
  plant 
  or 
  animal 
  body, 
  but 
  may 
  also 
  contain 
  excretions 
  

   from 
  decay 
  -producing 
  organisms. 
  Furthermore, 
  many 
  of 
  these 
  

   organisms 
  of 
  decay 
  have 
  themselves 
  died 
  and 
  decayed. 
  

  

  Processes 
  of 
  decay 
  are 
  of 
  great 
  biological 
  importance. 
  It 
  is 
  

   necessary 
  to 
  have 
  the 
  dead 
  bodies 
  and 
  the 
  waste 
  products 
  of 
  

   living 
  bodies 
  reduced 
  to 
  a 
  form 
  that 
  makes 
  their 
  removal 
  possi- 
  

   ble. 
  The 
  materials 
  that 
  are 
  broken 
  down 
  are 
  thus 
  made 
  usable 
  

   for 
  the 
  future 
  growth 
  of 
  plants 
  and 
  animals. 
  Without 
  decay 
  

   all 
  usable 
  food 
  material 
  would 
  eventually 
  be 
  rendered 
  unavail- 
  

   able 
  for 
  the 
  future 
  growth 
  of 
  plants 
  and 
  animals, 
  so 
  that 
  life 
  

   on 
  the 
  earth 
  would 
  cease. 
  The 
  earth's 
  supply 
  of 
  food 
  materials 
  

   would 
  be 
  locked 
  up 
  in 
  organized 
  plant 
  and 
  animal 
  bodies. 
  

  

  It 
  has 
  long 
  been 
  known 
  that 
  the 
  introduction 
  of 
  decayed 
  and 
  

   decaying 
  organic 
  matter 
  into 
  soils 
  enables 
  them 
  to 
  sustain 
  a 
  

   more 
  luxuriant 
  vegetation. 
  Undecayed 
  organic 
  matter 
  is 
  not 
  

   available 
  for 
  agricultural 
  or 
  horticultural 
  plants. 
  Such 
  material 
  

   must 
  await 
  more 
  complete 
  disorganization 
  before 
  it 
  can 
  be 
  use- 
  

   ful. 
  It 
  is 
  desirable 
  to 
  regulate 
  this 
  decomposition 
  so 
  that 
  the 
  

   largest 
  possible 
  amount 
  of 
  its 
  products 
  may 
  be 
  retained 
  in 
  the 
  

   soil. 
  This 
  is 
  one 
  of 
  the 
  problems 
  of 
  scientific 
  agriculture 
  (see 
  

   Chapter 
  XIX). 
  For 
  example, 
  if 
  stable 
  manure 
  in 
  large 
  masses 
  

   is 
  allowed 
  to 
  heat 
  under 
  the 
  rapid 
  destructive 
  action 
  of 
  the 
  bac- 
  

   teria 
  and 
  other 
  living 
  things 
  wliic-h 
  flourish 
  in 
  it, 
  much 
  valuable 
  

   ammonia 
  is 
  given 
  off 
  into 
  the 
  atmosphere 
  and 
  lost. 
  Slower 
  

   decay, 
  especially 
  if 
  underground, 
  wastes 
  but 
  little 
  ammonia. 
  

  

  191. 
  Bacteria 
  and 
  soils. 
  In 
  an 
  earlier 
  part 
  of 
  this 
  book 
  we 
  

   learned 
  that 
  nitrogen 
  compounds 
  are 
  necessary 
  for 
  the 
  con- 
  

   struction 
  of 
  part 
  of 
  the 
  food 
  which 
  plants 
  must 
  have. 
  In 
  the 
  

  

  